HEATING, VENTILATION & SERVICES 67


HYDRONIC HEATING: A SOLUTION FOR NET ZERO BUILDINGS


Gary Perry of Altecnic explores the advantages of using hydronic-based systems for heating future homes that are targeted to achieve much lower energy use


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here are many ways to provide space heating, cooling and domestic water heating in all-electric net zero buildings. They range from separate systems for each load, to integrated approaches that leverage energy recovery and energy management to minimise consumption and coordinate the needs of building occupants with the real time demand on the systems.


COMFORT FOR THE END USER Firstly, looking at thermal comfort, history has shown that approaches to space heating and cooling that require sacrifi ces in cofort to achieve hih eneryeffi ciency tarets or absolute minimum energy use, usually fail to gain sinifi cant arket share The lesson is that end-user comfort continues to be one of the most important underlying factors in establishing and maintaining a market for building energy systems.


Comfort is established when the conditions surrounding the body allow metabolic heat production to be dissipated at the same rate it is generated. Some degree of discomfort is experienced when these two rates of heat transfer are not balanced.


Several types of hydronic distribution systes siultaneously in uence air teerature, teerature stratifi cation and surface temperatures of rooms in ways that enhance human physiological comfort. Air-based delivery systems have less in uence on interior surface temperatures and can create undesirable drafts or air teerature stratifi cation As such, they are not as well matched to human comfort needs.


Acoustic comfort is also increasingly important – people want their home to be a quiet refuge from the pace and noise of modern life. They don’t want to hear sounds emanating from their heating and cooling systems. Properly designed and installed hydronic systems


A ‘homerun’ hydronic distribution system WWW.HBDONLINE.CO.UK


either outside the building or it can be acoustically isolated within a designated plant room.


Traditional hydronic heating system


using radiant panels or panel radiators can operate with virtually no detectable sound within occupied spaces. The sound produced by the source equipment, such as the compressor in a heat pump, is


DISTRIBUTION EFFICIENCY Professionals who design low energy and net zero buildings apply scrutiny when selecting the source equipment that supplies space heating, cooling and domestic hot water. They often limit selections to state-of-the-art devices with the hihest available theral effi ciencies While this approach is certainly relevant and logical, it is also incomplete. The energy used by the source equipment, be it a boiler, heat pump or chiller, is only part of the total energy used by the system. Regardless of how heating energy or cooling effect is generated, additional energy is needed to distribute that thermal energy within a building. Treating this distribution enery as insinifi cant or inconsequential is a serious oversight in the design process, especially when the objective is to create buildings that minimise energy use.


The energy required to distribute heat produced by any heat source, or the cooling effect generated by any cooling source, should always be considered when designing a heating or cooling system for a low energy or net zero building. Systems that use a sinifi cant aount of enery to move heat from where it is produced to where it is needed in the building are undesirable, even if the thermal energy is roduced at hih effi ciency by the source equipment.


Distribution energy is an even more important consideration for cooling systems. Every watt of electrical energy used to move the cooling effect through a building is a watt added to the building’s sensible cooling load.


Designers should also consider that air-to-air heat pumps typically require hiher air  ow rates er unit of heat delivery compared to fossil-fuel furnaces,


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